Operational DIffernce between the FLEX-6500 and 6700

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I am considering purchasing either the FLEX-6500 or FLEX-6700 but am having difficulty understanding (or appreciating) the difference between the two transceivers. Besides using higher speed processors the 6700 has two Spectral Capture Units (SCU). What is the real operational advantage of having two SCUs, considering the price difference between the two transceivers is $3,200?
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Bob - N7RJN

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Posted 5 years ago

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Tim - W4TME, Customer Experience Manager

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The FLEX-6700 has two (2) SCUs. The SCU is the wide band analog to digital converter (ADC) that converts RF to a binary format. Therefore you can only have one RX antenna connected to a single SCU at a time. If you have two independent RF to Binary signal paths, as you do with the FLEX-6700, then you can connect two separate antennas digitize RF in a diverse manner. This would allow you to perform diversity reception type techniques if the two antennas are of different (diverse) polarization and/or are 1/2 wavelength or greater distance apart from one another. Because of the diverse nature of the antennas (SCUs) receiving the RF, one of the two antennas will receive a signal of interest better than another, allowing for a higher performing reception process.

The FLEX-6500 has only one SCU, so diversity reception is not possible.

Also, due to the additional SCU and the increased computational capability of the FPGA and DSP processor in the FLEX-6700, once the spectrum is sampled (digitized) by an SCU, the software can create up to eight (8) "slice" receivers, whereas the FLEX-6500 has an upper limit of four (4).

There are some additional differences.

1.) Frequency coverage - The FLEX-6500, with one SCU has only one Nyquist "zone" so it can sample frequencies from 30 kHz to 77 MHz. The FLEX-6700 has two SCUs so it can have an additional Nyquist zone and will sample an additional frequency range of 135 to 165 MHz. This means that the FLEX-6700 covers the 2m band on RX in addition to the 30 kHz to 77 MHz range.

2.) Frequency stability and accuracy - The FLEX-6700 has an OCXO as the master oscillator (clock) and the FLEX-6500 has a TXCO as the master oscillator. Both oscillators provide exceptional frequency stability and accuracy, but the OCXO is better. If you chose to install the GPS disciplined oscillator (GPSDO) option, that provides even better frequency stability and accuracy in addition to being able to accurately time stamp the sampled spectrum data from the SCU.

3.) Preamp performance - The FLEX-6700 has a wider range of RF per-amplification and the preamps have a lower noise figure than the FLEX-6500. This is usually not a big differentiator in normal use since most hams live in areas that are noise limited and in those cases you will never need (or should use) the RF preamps unless you are operating on 12m and above in frequency. And in those cases, 10 dB of gain should be more than sufficient for optimal signal to noise.

A little more on the GPSDO option. Right now the advanced capabilities of having time stamped data is not available in the software, but in future versions of SmartSDR, you may be able to do things like using two separate FLEX-6000s for diversity reception since both radios will be using the same timebase for their master oscillators (GPS satellites). For now it provides greater frequency stability and accuracy for both the FLEX-6500 and FLEX-6700. This is an easy user installable upgrade that can be added at any time.

So those are the major differences between the FLEX-6500 and the FLEX-6700.
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Peter Bentley

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A very helpful explanation Tim, thank you

G4BIM

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sky

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Your list is accurate but the features are virtually esoteric and only meaningful and useable by the most ardent or competitive operators.  You mention seeing 8 bands at once,  2 meter coverage, lab standard stability, preamp performance. It is technologically impressive to see 8 bands at once but really, how long will you do it or use it before going to your favorite band(s)? Most 2 meter users have dedicated 2M rigs, the stability of 6500 has exceptionally stability. The preamp gain on the 6700 is somewhat greater but when you factor in how urban band noise level precludes using the extra gain. In fact, it extra gain become a liability under that scenerio. 
Flex knows exactly how the market is structured which is why they have three 6K models. The 6700 as feature laden that it is, for most people is serious overkill and priced too dear. The 6500 offers the most 'bang or the buck' and delivers an incredibly versatile, very high potent model. The price difference between 6500 and 6700 is $3,200. To put that another way, you must spend about 75% additional over the 6500 for the 6700.
(Edited)
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Ernest - W4EG

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And worth every penny to buy the 6700!
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George Molnar, KF2T, Elmer

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Having used a 6500 for the last couple of years (I pre-ordered and was an early recipient), I can say it's a great unit -- and it changes the way you think about operating. Stability opens up weak signal operation. Not that it's essential, but it does help. All those slices? I wish I had the "extra" ones a 6700 offers, especially since with two SCUs you can use optimized antennas for different bands simultaneously. Diversity is a great thing I wish I had - and suspect it will become a bigger selling point with advances in noise reduction that no doubt will come. Low noise preamps will work better without extra cable and stuff hanging off the rig (although never as good as at the antenna, I admit).

Worth noting is that I don't consider my 6000-series a "radio" as such. It is better described as a "radio server" that provides transmit and receive functions in a networked environment, which opens the doors to true remote use, multiple processors, and software flexibility. I notice most of the folks who are disappointed or frustrated with this technology are approaching it as they would a TS-520s or something similar. They're quite different. 

Maybe I am an "ardent or competitive operator." So be it. If I had to do it again, I would probably look for a way to swing the extra cost for the 6700. Either way, they are a pleasure to operate and really have opened up new experiences for me. If all you want is a casual rig that will provide many years of solid service, there are many options (including from Flex). Fine bunch of folks, they are.
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Walt - KZ1F

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Sky, personally, I think you nailed it. It is my observation that those that bought the 6700 did it because 'they could'. There was a poster on here a few weeks ago that said, in a similar conversation, in a very demeaning manner, "Well....not everybody can handle 8 bands at once, and, hihi, I must admit at times it requires an aspirin". That is completely nonsensical BS in my opinion. But there is a whole slew of people like that on here. Programatically (I have spent a career in software development) I could think of things to do in software like monitor all beacons to accurately identify when all the Amateur bands were open to what parts of the world.  That would be done in software not by a monolithic .NET application using a 42" monitor displaying 8 child windows and someone constantly changing the frequencies on each and making any sense whatsoever on what was displayed, with or without aspirin. And, programatically, you could do the same with 4 receivers. Diversity reception. I have yet to hear anyone, Flex user or Anan user say it is worth it's weight in gold. Sounds more to me like a 'because we could' solution looking for a problem. I could be wrong on that one but, is it worth another $4,000+ to find out?

I also preordered a 6500 and took a long hard look at which one I could get the most value out of as it likely would be my last radio. I just could not justify the 6700 price tag. I know other 6700 owners that off board acknowledged if they had to do it again they would have gotten a 6500.  The 6500 is an outstanding radio that, for the 4 receivers it does have, is pound for pound what the 6700 is.
Some people buy Tesla's because they can, some people buy BMW 7 series because they can. Some people have personal jets, because they can. So maybe it comes down to bragging rights. If you want to buy a really good radio, because you can, go for the 6700. If you want a supremely good radio, the 6500 is such a radio.
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Burt Fisher

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We are not your kids or grandkids and this is not texting
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Bill -VA3WTB

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Ernest, humor seems to be for only those who catch it, Hi Hi
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Dan -- KC4GO

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Sometimes it's worse than texting with the grand kid as FAR off topic as these threads get. Seeing as this is a Ham community I see no problem using any of the short cuts our society has developed over the years. If the meaning is not lost on the group you're addressing it works. with that a grand 73's to all and a -.-
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Walt - KZ1F

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Now you're just testing our CW pronoun understanding huh Dan?
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Walt - KZ1F

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Now you're just testing our CW pronoun understanding huh Dan?
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Norm - W7CK

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I have the 6700 and it is a very good rig.  I have never operated the 6500, so I can't say if the 6700 out performs it or not.  I find it hard to believe anyone could actually tell the difference in receive of  a weak signal between the two rigs.

The 6700 includes VHF.  This may be a good thing or may not.  If you already have a dedicated VHF rig and you don't use SSB, then it really isn't much of a plus.  2 meters operation on the 6700 at present is a PITA for the most part.  At least until the software matures......  Until then, you are stuck with constantly battling with the rig trying to select a different antenna and band.  Its extreamly difficult to use 2m and other bands at the same time.  Too many quirks using the present software.  Once again - it will only get better with time.  I think one would be far ahead using a good transverter if they want the Flex on 2 meters.  Otherwise, I'd recommend using a dedicated 2 meter rig. Most 2 meter or multi-band shack-in-a-box rigs that include VHF also have UHF, they can scan frequencies and or entire band segments, they have a squelch function that actually works.  Flex's sql is ok but it often breaks sql for no apparent reason.  So what you get is a bunch of squaks all day long on an otherwise quiet frequency.  There is no way to scan frequencies yet on the flex so you are stuck with dedicating a slice to each frequency you want to monitor.  Since the 6700 gives you 8 slices, you may find this adequate.

The other thing the 6700 gives you is diversity.  If you have more than one HF antenna and can use diversity, this may be the deciding factor for you.  I've used it with dipoles and verticals and it works fairly well.  As the software develops, this function should only get better.

If I had it over, I guess I would still get the 6700 because I trust Flex to continue to develop the software to the point the 6700 will be supreme.  For me, I had the money and it was my retirement present to myself.  If money is just a tad tight, I'd get the 6500 and I'm sure you will be just as happy with it.  I personally don't think the 6700 offers enough to justify the additional cost.  I know - I'm contridicting myself a bit, but that's just the way it is......
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Walt - KZ1F

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I will just comment really quickly as you pinned this to, "if you can't afford the 6700". Two meters: I doubt 1mw really constitutes a 2m radio. I don't see the value in that. If someone wanted a 2m rig, they'd look for something other than 1mw. I wouldn't pay an additional $4,000 for a 1mw 2m radio. I think DR with geographically distant stations holds great promise. DR in your backyard. Isn't that a little like circular polarization? I've got a vertical for 15 and a 15m yagi so I put the two together. My previous comment was prefaced with "I've yet to hear anyone say that...". So if a couple of people like it, the question one has to ask themselves is 'do I want to pay $4,000 for it". If the answer to that question is no, it is not a lack of money, it is a lack of interest. I think people on here should disabuse themselves of the notion people who don't buy a 6700 aren't as wealthy or as smart or as capable. That is snobbish, egocentric and completely false. Perhaps they are wealthier and smarter as they don't fritter their money away on unnecessary or questionable 'features'. Everyone on here that pre-ordered a 6000 series radio, placed a bet, pure and simple. I, among them.
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Ernest - W4EG

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Norm,

Your statement " I personally don't think the 6700 offers enough to justify the additional cost."  I agree with your contradiction.
However, we all gamble when Flex introduced the new Flex-6000 line of radio. We were placing bets on the idea that this line of radios would "eventually in it's due time" be the best radio available. As far as I am concerned it is.  
No Collins, Signal One, Drake, Yaesu, Icom etc are even close to the performance of the 6700. I've owned the above radio plus many of the other American and rice paddy units in the last 55 plus years. 
Flex the way to the future today!
(Edited)
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Norm - W7CK

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Even though I feel that it may not be worth the additional $.  I'm not parting with my 6700 any time soon!  I've spent my money and I'm not looking back.  I love having 2 antennas active and monitoring several different bands at the same time, diversity, a great preamp, wonderful zoom, 2 meters which I actually use (I paired it with a 2N75 LDPA from Down East).  2 meters, FM and SQL all need some additional attention, but they do work. Like everyone in the FRS boat, we look forward to each new software release where most just keep getting a little bit better. 

Would I have been happy with a 6500 - heck yah!  Its a great rig too! 
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Walt - KZ1F

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Earnest, Yep! Right now, most of us on here,  ARRL Labs, SherwoodEngineering, the 6[5|7]00 are the best radios available. The 6300 is in the top 10 as I recall. Nothing is static, everything changes.
The irony I think is, and this is just my prognostication, when FRS announces the 7000, the phone lines will be busy with most 6700 owners ordering the 7000 series. The underlying thing there is the notion of what someone perceives to be better and their drive to have the best, which will always change. The 6500 is a really, really, really good radio and if I live another 20 or 30 years, it will still be an equally good radio.  I stand corrected Ken, $3200 then. I bought the GPSDO so the 6700 offers no stability that my 6500 doesn't. When the DR comes not from a second local ant but the internet, I, too, will have DR. Again, using the radio telescope model.
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Ken - NM9P, Elmer

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My opinion... I own a 6500, but wish I could have afforded a 6700. I addition to processor speed, stability, etc. the features I would have in an upgrade would be:

1). Ability to monitor different bands on different antennas at the same time....I.e. 160 and 10 or 6, or even 2 meter. Yes, I can monitor four frequencies at once, but only on one antenna. Big difference.

2) diversity...simple now, more complex methods will come later.

3). 2 meter coverage. Yes it is low power, but I have played with a transverter and using a large pan adapter on 2 meters is really neat.

4) twice the number of pans and receiver slices. More versatility. Especially with two different antennas.

The 6700 is $3200 U.S. more than the 6500. A lot, but you are essentially getting two 6500's with additional features also....deeper zoom on receive, Better preamp, and others.

But the 6500 is a fine, fine rig.

Ken - NM9P
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Ken - NM9P, Elmer

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No argument there, Steve!  I live in Indiana.  We get a lot of lightning, too.  I lost a DirecTV Satellite dish, cordless phone, and two computer modems to a strike back in 1998.  Two years ago I lost a DSL Modem, Router, and a BluRay DVD player that all got sandwiched between the powerline and CAT5/DSL Line.  Thankfully none of the ham equipment was damaged.

This is the one thing about my pending antenna tower project that has me nervous...knowing that I may be a bigger target for lighting.  Even though I will be taking steps for tower grounding, lightning arrestors, binding the AC safety ground, tower ground, etc......  I also need to raise my insurance coverage!

Ken - NM9P
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Stan - VA7NF

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Actually Ken you may be safer with the tower as you can direct that lightning directly to ground and not through everything else. 

It is not the rise in voltage on your ground but the surge voltage difference that causes the problem.  Lightning ground at the tower and RF ground + surge protectors at the cable entry are very effective (at least 8' separation between tower and RF or safety ground will pick up the rise of earth voltage and feed it into the house)

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Walt - KZ1F

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@SteveM They do have equipment insurance through ARRL. Also, it is not clear if homeowners insurance would cover it. Certainly you could get a rider for it, just as for expensive jewelry. But if you unplug power and coax you should be fine.
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SteveM

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Thanks, Walt. I've looked into insurance to cover personal items. It turned out to be cost prohibitive. I opted for the manual insurance that you suggested. One must be very diligent for that method to be effective.
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Walt - KZ1F

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As I recalled that is services through Hayes or Hays. I just had to renew it for the policy period of end of May to end of Apr. I have the 1500, 6500, rotor, TS-530, KPA500 and KAT500 insured. It's pricey but, as you pointed out, way less pricey than ordering a new 6500. AS it turns out, my rotor did break. knock wood I haven't had a strike at this qth.
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W7NGA

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I'm so old school I guess ... love the 'clunk' of the bandswitch on my Collins 75A4 or R390A. One band at a time .. love the mystery of what I might find. Just noise? 'Kerchunk', tweak the antenna trimmer and I'm good to go. Hardly break a sweat. Might even play with the BFO knob ...

dan W7NGA
San Juan Island, Wa.
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Norm - W7CK

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Hey Dan,
I have a couple older rigs here as well as some newer ones.  I love the clunk of the switches and the smell and heat from the tubes on a winter night.  I also like the new technology and am really looking forward to what will be coming out on the market in the next couple years.

What I'd really like to see is a ruggedized, portable SDR with knobs, internal 10:1 tuner and internal lithium battery pack. QRP to maybe 20 watts, good heat sink and no cooling fan.  Sort of like the KX3 but I want all of the cables coming out the back of the rig instead of out the sides and looking like an octopus.  One band at a time with knobs, or hook it up to a computer and use like one of the 6000 series rigs.  

Just dreaming....
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Barry N1EU

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sign me up for one of those Norm, as long as it comes in no heavier or current hungry than the KX3, which is a tall order

73, Barry N1EU